Medical equipment for radiation therapy treats tumorous tissue with high energy radiation. In external source radiation therapy, a radiation source external to the patient treats internal tumors. The external source is normally collimated to direct a beam only to the tumor location. Typically, the radiation source consists of either high-energy X-rays, electrons from certain linear accelerators, or gamma rays from highly focused radioisotopes.
The dose and the placement of the dose must be accurately controlled to insure both that the tumor receives sufficient radiation to be destroyed and that damage to the surrounding and adjacent non-tumorous tissue is minimized. To properly plan and perform a radiation therapy treatment session, tumors and adjacent normal structures can be delineated in three-dimensions using specialized hardware and software. For example, intensity modulated radiation therapy (“IMRT”) treats a patient with multiple rays of radiation each of which may be independently controlled in intensity and/or energy. The rays are directed from different angles about the patient and combine to provide a desired dose pattern. The desired dose pattern is determined and optimized based on the three-dimensional shape of the tumorous tissue.
Conventional IMRT optimization, however, has some costs. For example, IMRT optimization generally requires the use of sophisticated, expensive hardware and software. In addition, the computer processing required for IMRT optimization can be time-consuming, such that full treatment planning and optimization cannot be performed under time constraints. Approximations may be used to increase the processing time of IMRT optimization, but these can reduce the accuracy of the optimization. Furthermore, conventional IMRT optimization only accounts for beamlet parameters or voxel parameters and fails to take other parameters, such as machine parameters, into account.